The present invention relates to an optical device and a method of manufacturing a device. Such a device provides accurately aligned optical paths and may be used in association with a micromachined structure, such as a silicon bridge to form a transducer, or with devices where optical alignment is required.
Pages 186 to 189 of a philosophical dissertation by Rudolf A. Buser submitted to the University of Neuchatel, Switzerland, entitled "Theoretical and Experimental Investigations on Silicon Single Crystal Resonant Structures" disclose an arrangement for illuminating a resonant beam cantilever with optical radiation from an optical fibre. The fibre is located in a groove of V-shaped cross section formed by etching from a surface of monocrystalline silicon aligned in a {100} crystallographic plane. The end of the optical fibre faces a mirror surface formed by etching to reveal a transverse surface in one of the {111} crystallographic planes. The cantilever is formed above the mirror surface such that optical radiation, such as visible light or infrared radiation, emitted from the end of the fibre is reflected by the mirror surface onto the cantilever. This arrangement functions as a resonant beam transducer, for instance for measuring pressure.
Because of the crystallographic alignment of the mirror surface with respect to the main surface of the device, the optical axis of the fibre intersects the mirror surface at an angle of 54.7.degree.. The cantilever is arranged such that the reflected radiation from the mirror surface is incident on the cantilever. However, reflected radiation from the cantilever is substantially not reflected back along the optical axis of the fibre, so that separate means are required in order to monitor the resonant frequency of the cantilever, which resonant frequency is a function of the applied pressure or other parameter to be measured.
US 5 071 213 discloses a similar arrangement for coupling an optical fibre to an opto-electronic device. The fibre is held in a groove of V-shaped cross section formed by etching a working surface of a silicon substrate aligned in a &lt;100&gt; direction. The end of the fibre is held adjacent a transverse surface. The transverse surface is at an angle of approximately 55.degree. with respect to the working surface. Light from the fibre is directed towards the transverse surface, from where it is reflected to the opto-electronic device.